Craig Nichol

Environmental risk assessment of acid rock drainage under uncertainty: The probability bounds and PHREEQC approach.

Acid rock drainage (ARD) is a major environmental problem that poses significant environmental risks during and after mining activities. A new methodology for environmental risk assessment based on probability bounds and a geochemical speciation model (PHREEQC) is presented. The methodology provides conservative and non-conservative ways of estimating risk of heavy metals posed to selected endpoints probabilistically, while propagating data and parameter uncertainties throughout the risk assessment steps. The methodology is demonstrated at a minesite located in British Columbia, Canada. The result of the methodology for the case study minesite shows the fate-and-transport of heavy metals is well simulated in the mine environment. In addition, the results of risk characterization for the case study show that there is risk due to transport of heavy metals into the environment.

Modelling spatial association in pattern based land use simulation models.

Pattern based land use models are widely used to forecast land use change. These models predict land use change using driving variables observed on the studied landscape. Many of these models have a limited capacity to account for interactions between neighbouring land parcels. Some modellers have used common spatial statistical measures to incorporate neighbour effects. However, these approaches were developed for continuous variables, while land use classifications are categorical. Neighbour interactions are also endogenous, changing as the land use patterns change. In this study we describe a single variable measure that captures aspects of neighbour interactions as reflected in the land use pattern. We use a stepwise updating process to demonstrate how dynamic updating of our measure impacts on model forecasts. We illustrate these results using the CLUE-S (Conversion of Land Use and its Effects at Small regional extent) system to forecast land use change for the Deep Creek watershed in the northern Okanagan Valley of British Columbia, Canada. Results establish that our measure improves model calibration and that ignoring changing spatial influences biases land use change forecasts.

Irrigation practices, nutrient applications, and mulches affect soil nutrient dynamics in a young Merlot (Vitis vinifera L.) vineyard

Abstract: There is growing interest among commercial wine grape (Vitis vinifera L.) growers in reducing water and fertilizer consumption, but little information exists on how best to combine conservative irrigation and soil management practices in the vineyard. In a 3-year-old Merlot vineyard in the semi-arid Okanagan Valley, British Columbia, the interactive effects of resource-conserving micro-irrigation (drippers or microsprinkers), nutrient applications (fertigation or compost), and surface mulching (wood and bark chips) on nitrogen (N) and phosphorus (P) dynamics in the wetted zone of surface soils were examined throughout the growing season using ion-exchange resins. Treatment differences in soil carbon and major nutrient pools, temperature, and moisture were also measured. Higher NO3-N was adsorbed by resins buried under drippers than under microsprinklers except in mulched plots, where NO3-N was uniformly low. By enhancing soil carbon availability and moderating soil microclimate, surface mulches may have promoted microbial immobilisation of N. Compost applications increased soil ortho-P levels, especially on mulched plots, suggesting that both P inputs (from compost) and enhanced microbial biomass (from mulch) promoted soil P cycling. Future work will examine the interactive effects of these resource-efficient practices on leaching losses, greenhouse gas emissions, crop productivity, and fruit quality.

A low cost and flexible open source communications framework for temporally aligned sampling in distributed sensing systems

The ability to understand phenomena in environmental systems is reliant on the ability to measure data about the system. In this realm, a high degree of non-homogeneity can exist between adjacent measurement points. The barrier to increased spatial sampling is device cost. Newer low-cost sampling platforms enable increased spatial sampling allowing for a better understanding of phenomena. Many sensing applications also require temporal synchronization across distributed devices to understand phenomena. This work presents a novel, low cost and flexible communications framework built on open source technologies with a sample application. It allows for multiple devices to be connected via a bus topology and controlled and addressed from a single master device. A time synchronization strategy is presented that allows for low cost devices to be used for temporally aligned sampling without the need for complex and expensive time synchronization equipment. The wired system is based on the proven and robust RS-485 physical layer, and addresses numerous issues that are often encountered with other technologies. The sample application of low range differential pressure measurements demonstrates the functionality of both hardware and software components. This paper describes the design and implementation of the communications framework that can be used to measure distributed sensors with low cost, temporal alignment of data. The communications framework is available at https://github.com/sensingFramework.

A simple approach for determining mountain system recharge in arid and semi-arid mountainous watersheds: A quasi steady state groundwater model with sensitivity analysis

Mountain system recharge is the dominant source of recharge to alluvial aquifer system in arid and semiarid mountainous regions. Based on the field and historical data, a quasi steady state numerical groundwater model with sensitivity analysis was developed with FEFLOW to assess mountain system recharge to a multi-layer aquifer system in North Okanagan located in the semi-arid southern interior of British Columbia, Canada. The sensitivity analysis indicates that mountain system recharge varies from 5.0% to 6.6% of precipitation on the mountains. This results in modeled mountain block recharge to the valley bottom moderated and deep aquifers of about 3.6 % to 4.8% of precipitation on the mountains.